text: The Radium Dial Company was one of a few now defunct United States companies, along with the United States Radium Corporation, involved in the painting of clocks, watches and other instrument dials using radioluminescent paint containing radium. The resulting dials are now collectively known as radium dials. The luminous paint used on the dials contained a mixture of zinc sulfide activated with silver, and powdered radium, a product that the Radium Dial Company named Luma.  However, unlike the US Radium Corporation, Radium Dial Company was specifically set up to only paint dials, and no other radium processing took place at the premises.